1. Field of the Invention
The present invention relates to an image forming method using an inkjet method.
2. Description of the Related Art
In recent years, regarding methods of recording images, there is a demand for obtaining high-quality images in a wide variety of common situations no matter which method is used. For example, in ink jet techniques, there is an image recording method which is widely anticipated in the fields such as office printers, home printers and the like and in the commercial field since the desired image forming on various target recording mediums can be performed.
As ink which is used in ink jet recording, other than solvent type ink, from the point of considering the global environment or business environment, water type inks have gained attention. Even among such water type inks, a technique is being examined where a highly scratch resistant image is formed due to curing by including a polymerizable monomer component in a water-based pigment ink. As one such image forming technique, for example, an ink jet recording method is disclosed where ultra violet rays (UV) are irradiated for a predetermined time period after ink is landed on a substrate, using an ultra violet curable ink which contains coloring material, ultra violet polymerizable material, and a photoinitiator in an aqueous medium (for example, refer to JP2004-209976A).
In addition, as the method of curing by including a polymerizable monomer component, there is a technique where the monomer component is thermal polymerized. For example, an ink jet recording method is disclosed where heating is performed after printing using ink on recording media where a pigment layer is coated onto a support in which cellulose pulp is a main component (for example, refer to JP2008-100511A and JP2011-42150A).
Among techniques in the related art described above, in a method of performing ultra violet ray irradiation for a predetermined time after ink landing, film properties (scratch resistance, water resistance) and suppression of paper deformation (curl) are increased by exposure before the ink is absorbed in the paper, but it is difficult to obtain a desired curing sensitivity. That is, with regard to water-based inks of a UV curing type, it is understood that appropriate drying is important for obtaining excellent exposure sensitivity, and sufficient sensitivity cannot be obtained with exposure immediately after ink landing as described above. Moreover, in UV irradiation immediately after ink landing, the setting positions of a UV light source and a discharge head become closer, ink in the vicinity of a discharge hole is cured by light leakage from the UV light source, and as a result, this is a cause of damage to the head. Therefore, the risk in terms of the system is extremely high.
In addition, in a thermal curing method, since water derived from the ink or a water-soluble organic solvent largely remains in a pigment layer (that is, a coated layer of a coated paper) after printing, the strength of the pigment layer is remarkably easily decreased, and not only does the layer itself weaken, but the adhesion of the image and the strength of the image itself become problems. In this method, since the aqueous medium is volatized or diffused into the pulp by the recording media being left for a time after the image forming and the remaining amount of water or solvent in the coated layer is reduced, the reduction and the like in the strength of the pigment layer is alleviated; however, this requires being left for a time of one day or more. Processing or the like cannot be carried out immediately after printing in practice.
In addition, when recording an image, there is a demand that various types of unevenness not be generated. In particular, in terms of the external appearance, gloss unevenness which is made to stand out by the reflection of light is a cause of a remarkable decrease in product quality. For the improvement of such gloss unevenness, generally, it is advantageous when the curing speed during the curing is faster; however, for this reason, it is essential to promote the curing by imparting a certain degree of illuminance. Therefore, it is desirable to provide a curing system in which the curing of the image proceeds rapidly even at a low illuminance and in which gloss unevenness is not easily generated, and the technical significance of the provision of such a curing system is great.